Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1703.00359 · Physical Review A

Double resonance of Raman transitions in a degenerate Fermi gas

Moosong Lee, Jeong Ho Han, Jin Hyoun Kang, Minseok Kim, Yong-il Shin

Published Apr 20, 2017• 9 citations
arXivHTMLPDF

Abstract

Momentum-resolved Raman spectra of a spin-polarized Fermi gas of ytterbium atoms are measured, and it is found that double resonances of first- and second-order Raman transitions can occur at certain magnetic fields. This implies that the conventional Raman laser dressing scheme provides two ways of spin-orbit coupling, and intrinsically generates a spinful band structure without the aid of an additional rf field.

DOI
10.1103/physreva.95.043627

Related papers

Spin-orbit coupling in Bose-Einstein condensate and degenerate Fermi gases

Pengjun Wang, Jing Zhang

We review our recent experimental realization and investigation of a spin-orbit (SO) coupled Bose-Einstein condensate (BEC) and quantum degenerate Fermi gas. By using two counter-propagating Raman lasers and controlling the different frequency of two Raman lasers to engineer the atom-light interaction, we first study the SO coupling in BEC. Then we study SO coupling in Fermi gas. We observe the spin dephasing in spin dynamics and momentum distribution asymmetry of the equilibrium state as hallmarks of SO coupling in a Fermi gas. To clearly reveal the property of SO coupling Fermi gas, we also study the momentum-resolved radio-frequency spectroscopy which characterizes the energy-momentum dispersion and spin composition of the quantum states. We observe the change of fermion surfaces in different helicity branches with different atomic density, which indicates that a Lifshitz transition of the Fermi surface topology change can be found by further cooling the system. At last, we study the momentum-resolved Raman spectroscopy of an ultracold Fermi gas.

Frontiers of Physics•Oct 1, 2014•10 citations

Raman-dressed spin-1 spin-orbit-coupled quantum gas

Zhihao Lan, Patrik Öhberg

The recently realized spin-orbit-coupled quantum gases [Lin et al., Nature (London) 471, 83 (2011); Wang et al., Phys. Rev. Lett. 109, 095301 (2012); Cheuk et al., Phys. Rev. Lett. 109, 095302 (2012)] mark a breakthrough in the cold atom community. In these experiments, two hyperfine states are selected from a hyperfine manifold to mimic a pseudospin-1/2 spin-orbit-coupled system by the method of Raman dressing, which is applicable to both bosonic and fermionic gases. In this paper, we show that the method used in these experiments can be generalized to create any large pseudospin spin-orbit-coupled gas if more hyperfine states are coupled equally by the Raman lasers. As an example, we study, in detail, a quantum gas with three hyperfine states coupled by the Raman lasers and show, when the state-dependent energy shifts of the three states are comparable, triple-degenerate minima will appear at the bottom of the band dispersions, thus, realizing a spin-1 spin-orbit-coupled quantum gas. A novel feature of this three-minima regime is that there can be two different kinds of stripe phases with different wavelengths, which has an interesting connection to the ferromagnetic and polar phases of spin-1 spinor Bose-Einstein condensates without spin-orbit coupling.

arXiv:1311.6177•Physical Review A•Feb 24, 2014•90 citations

Magnetic-Field Dependence of Raman Coupling Strength in Ultracold 40 K Atomic Fermi Gas

Lianghui Huang, Pengjun Wang, Zengming Meng +4 more

We experimentally demonstrate the relation of Raman coupling strength with the external bias magnetic field in degenerate Fermi gas of 40 K atoms. Two Raman lasers couple two Zeeman energy levels, whose energy splitting depends on the external bias magnetic field. The Raman coupling strength is determined by measuring the Rabi oscillation frequency. The characteristics of the Rabi oscillation is to be damped after several periods due to Fermi atoms in different momentum states oscillating with different Rabi frequencies. The experimental results show that the Raman coupling strength will decrease as the external bias magnetic field increases, which is in good agreement with the theoretical prediction.

Chinese Physics Letters•Mar 1, 2016•1 citation

Density-dependent spin-orbit coupling in degenerate quantum gases

Peng Xu, Tian-Shu Deng, Wei Zheng +1 more

In this letter we propose a method to realize a kind of spin-orbit coupling in ultracold Bose and Fermi gases that depends on the density of atoms. Our method combines two-photon Raman transition and periodical modulation of spin-dependent interaction, which gives rise to both the direct Raman process and the interaction-assisted Raman process. The interaction-assisted Raman process depends on the density of atoms. These two processes have opposite effects in terms of spin-momentum locking and compete with each other. As the interaction modulation increases, the system undergoes a crossover from the direct Raman process dominated regime to the interaction-assisted Raman process dominated regime. During this crossover, for bosons, both the condensate momentum and the chirality of condensate wave function change sign, and for fermions, the Fermi surface distortion is inverted. We highlight that there exists an emergent spatial reflectional symmetry in the crossover regime, which can manifest itself universally in both Bose and Fermi gases. Our method may pave a way to novel phenomena in the density-dependent spin-orbit coupling gauge field with intrinsic dynamics.

arXiv:2007.05999•Physical Review A•Jun 14, 2021•9 citations

Momentum-resolved radio-frequency spectroscopy of ultracold atomic Fermi gases in a spin-orbit-coupled lattice

Xia-Ji Liu

We investigate theoretically momentum-resolved radio-frequency (rf) spectroscopy of a noninteracting atomic Fermi gas in a spin-orbit coupled lattice. This lattice configuration has been recently created at MIT [Cheuk et al., Phys. Rev. Lett. 109, 095302 (2012)] for ${}^{6}$Li atoms, by coupling the two hyperfine spin states with a pair of Raman laser beams and additional rf coupling. Here, we show that momentum-resolved rf spectroscopy can measure single-particle energies and eigenstates and therefore resolve the band structure of the spin-orbit coupled lattice. In our calculations, we take into account the effects of temperatures and harmonic traps. Our predictions are to be confronted with future experiments on spin-orbit coupled Fermi gases of ${}^{40}$K atoms in a lattice potential.

arXiv:1206.4778•Physical Review A•Sep 13, 2012•7 citations

In situ momentum-distribution measurement of a quantum degenerate Fermi gas using Raman spectroscopy

Constantine Shkedrov, Gal Ness, Yanay Florshaim +1 more

The ability to directly measure the momentum distribution of quantum gases is both unique to these systems and pivotal in extracting many other important observables. Here we use Raman transitions to measure the momentum distribution of a weakly interacting Fermi gas in a harmonic trap. For narrow atomic dispersions, momentum and energy conservation imply a linear relation between the two-photon detuning and the atomic momentum. We detect the number of atoms transferred by the Raman beams using sensitive fluorescence detection in a magneto-optical trap. We apply this technique to a degenerate weakly interacting Fermi gas at different temperatures. The measured momentum distributions match theoretical curves over two decades, and the extracted temperatures are in very good agreement with the ones obtained from a conventional time-of-flight technique. The main advantages of our measurement scheme are that it can be spatially selective and directly probe a trapped gas, it can be completed in a relatively short time, and due to its high sensitivity, it can be used with very small clouds.

arXiv:1909.12141•Physical Review A•Jan 10, 2020•8 citations
Momentum-resolved Raman spectra of a spin-polarized Fermi gas of ytterbium atoms are measured, and it is found that double resonances of first- and second-order Raman transitions can occur at certain magnetic fields. This implies that the conventional Raman laser dressing scheme provides two ways of spin-orbit coupling, and intrinsically generates a spinful band structure without the aid of an additional rf field.
We review our recent experimental realization and investigation of a spin-orbit (SO) coupled Bose-Einstein condensate (BEC) and quantum degenerate Fermi gas. By using two counter-propagating Raman lasers and controlling the different frequency of two Raman lasers to engineer the atom-light interaction, we first study the SO coupling in BEC. Then we study SO coupling in Fermi gas. We observe the spin dephasing in spin dynamics and momentum distribution asymmetry of the equilibrium state as hallmarks of SO coupling in a Fermi gas. To clearly reveal the property of SO coupling Fermi gas, we also study the momentum-resolved radio-frequency spectroscopy which characterizes the energy-momentum dispersion and spin composition of the quantum states. We observe the change of fermion surfaces in different helicity branches with different atomic density, which indicates that a Lifshitz transition of the Fermi surface topology change can be found by further cooling the system. At last, we study the momentum-resolved Raman spectroscopy of an ultracold Fermi gas.
The recently realized spin-orbit-coupled quantum gases [Lin et al., Nature (London) 471, 83 (2011); Wang et al., Phys. Rev. Lett. 109, 095301 (2012); Cheuk et al., Phys. Rev. Lett. 109, 095302 (2012)] mark a breakthrough in the cold atom community. In these experiments, two hyperfine states are selected from a hyperfine manifold to mimic a pseudospin-1/2 spin-orbit-coupled system by the method of Raman dressing, which is applicable to both bosonic and fermionic gases. In this paper, we show that the method used in these experiments can be generalized to create any large pseudospin spin-orbit-coupled gas if more hyperfine states are coupled equally by the Raman lasers. As an example, we study, in detail, a quantum gas with three hyperfine states coupled by the Raman lasers and show, when the state-dependent energy shifts of the three states are comparable, triple-degenerate minima will appear at the bottom of the band dispersions, thus, realizing a spin-1 spin-orbit-coupled quantum gas. A novel feature of this three-minima regime is that there can be two different kinds of stripe phases with different wavelengths, which has an interesting connection to the ferromagnetic and polar phases of spin-1 spinor Bose-Einstein condensates without spin-orbit coupling.
We experimentally demonstrate the relation of Raman coupling strength with the external bias magnetic field in degenerate Fermi gas of 40 K atoms. Two Raman lasers couple two Zeeman energy levels, whose energy splitting depends on the external bias magnetic field. The Raman coupling strength is determined by measuring the Rabi oscillation frequency. The characteristics of the Rabi oscillation is to be damped after several periods due to Fermi atoms in different momentum states oscillating with different Rabi frequencies. The experimental results show that the Raman coupling strength will decrease as the external bias magnetic field increases, which is in good agreement with the theoretical prediction.
In this letter we propose a method to realize a kind of spin-orbit coupling in ultracold Bose and Fermi gases that depends on the density of atoms. Our method combines two-photon Raman transition and periodical modulation of spin-dependent interaction, which gives rise to both the direct Raman process and the interaction-assisted Raman process. The interaction-assisted Raman process depends on the density of atoms. These two processes have opposite effects in terms of spin-momentum locking and compete with each other. As the interaction modulation increases, the system undergoes a crossover from the direct Raman process dominated regime to the interaction-assisted Raman process dominated regime. During this crossover, for bosons, both the condensate momentum and the chirality of condensate wave function change sign, and for fermions, the Fermi surface distortion is inverted. We highlight that there exists an emergent spatial reflectional symmetry in the crossover regime, which can manifest itself universally in both Bose and Fermi gases. Our method may pave a way to novel phenomena in the density-dependent spin-orbit coupling gauge field with intrinsic dynamics.
We investigate theoretically momentum-resolved radio-frequency (rf) spectroscopy of a noninteracting atomic Fermi gas in a spin-orbit coupled lattice. This lattice configuration has been recently created at MIT [Cheuk et al., Phys. Rev. Lett. 109, 095302 (2012)] for 6{}^{6}6Li atoms, by coupling the two hyperfine spin states with a pair of Raman laser beams and additional rf coupling. Here, we show that momentum-resolved rf spectroscopy can measure single-particle energies and eigenstates and therefore resolve the band structure of the spin-orbit coupled lattice. In our calculations, we take into account the effects of temperatures and harmonic traps. Our predictions are to be confronted with future experiments on spin-orbit coupled Fermi gases of 40{}^{40}40K atoms in a lattice potential.
The ability to directly measure the momentum distribution of quantum gases is both unique to these systems and pivotal in extracting many other important observables. Here we use Raman transitions to measure the momentum distribution of a weakly interacting Fermi gas in a harmonic trap. For narrow atomic dispersions, momentum and energy conservation imply a linear relation between the two-photon detuning and the atomic momentum. We detect the number of atoms transferred by the Raman beams using sensitive fluorescence detection in a magneto-optical trap. We apply this technique to a degenerate weakly interacting Fermi gas at different temperatures. The measured momentum distributions match theoretical curves over two decades, and the extracted temperatures are in very good agreement with the ones obtained from a conventional time-of-flight technique. The main advantages of our measurement scheme are that it can be spatially selective and directly probe a trapped gas, it can be completed in a relatively short time, and due to its high sensitivity, it can be used with very small clouds.